


You Make Me All Achy

by Emela



Category: Teen Wolf (TV)
Genre: Angst with a Happy Ending, Blow Jobs, Fairy Tale Elements, First Kiss, Hand Jobs, M/M, Merman Stiles, Porn With Plot, Slightly Dark Stiles, Soulmates, Stiles has a very sensitive tail
Language: English
Status: Completed
Published: 2015-04-09
Updated: 2015-04-09
Packaged: 2018-03-22 02:31:57
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 10,965
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3711520
Author URL: https://archiveofourown.org/users/Emela/pseuds/Emela
Summary: <blockquote class="userstuff">
              <p>
  <em>It was only when Derek’s head broke the water’s surface, he realised what was happening - he was being pulled under - and pushing against the boy, flung himself back out of reach, breathing heavily- from fear or the kiss, he couldn’t tell. </em>
</p><p>
  <em>“What-” he began to ask but the boy raised his hand, cutting him off, staring at Derek wide-eyed, a look of great surprise on his face, before vanishing into the lake.</em>
</p><p>
  <em>It was then that Derek saw it; the golden, red tail where a pair of legs should have been.</em>
</p><p>OR</p><p>The one in which Stiles is a merman, tries to drown Derek, but when he kisses him falls in love with him instead. (Oh, Stiles.)</p>
            </blockquote>





	You Make Me All Achy

**Author's Note:**

> Anon asked for a Sterek mermaid AU and this happened. I don't know whether to apologise in advance or not. I really do not know how I managed to turn a mermaid fic into smut...I truly worry about myself sometimes. The plot, as true to fairy tale form, escalates rather quickly but I hope you enjoy it, regardless!

The first thing Derek remembered his mom ever telling him was,  _ do not go where the wall is. _

He had never been the type of child to question his parents, especially his mother. He didn’t get any joy from defying them, and despite the constant pull he always felt towards the wall, his parents’ death dampened any temptation he had had to disobey their last wish to him.

His resolve to stay away lasted until his twenty-first birthday. 

There was nothing extraordinary about the day itself, if you ignored it was the day he was born - which Derek often did; nor did he wake up with a sudden, irrepressible urge to finally see what lay at bottom of the family gardens. Most of the day passed as every other Birthday had before- with a cake, people, and Laura and Cora making silly faces at him as Derek forced his way through smile after smile, greeting the parade of Princesses and Princes who came to wish him “many happy returns”. 

It was a parade carefully selected by his Uncle, as it was every year. Derek could think of few things he hated more; the guest list was the same every year, the same faces depressing him further and further, knowing, one day, he would have to marry one of them- someone he did not love- in order to make an alliance with the Kingdom his Uncle chose.

He danced, having no other choice, but he couldn’t bring himself to talk to anyone - at least, no more than was polite - but it wasn’t until Derek was getting ready for bed, claiming a headache, did he remember the wall’s existence at all.

Crossing to the other side of his bedroom, he opened his window and looked out into the night. The whole kingdom was lit up in honour of his birthday; the festivities would no doubt last until tomorrow and, gazing down, Derek was suddenly struck with a terrifying thought: what is this was the only opportunity to see the wall before he was sent to live in another kingdom? He was twenty one now, and not many princes in Derek’s position were granted the freedom of staying with their families long out of their teens. Derek supposed he should count himself lucky his Uncle had chosen to give him this long. 

He took a moment to pause, guilt churning his stomach, his parents’ faces playing on his mind; but after tonight, after being continually showcased to every “potential match” Peter had deemed “worthy” - shown off like prized pig or horse - Derek needed this. He needed to do something for himself. 

Just this once, he wanted to do something  _ he _ wanted to do, not because someone ordered him to, and disobeying an order - an order Peter reminded him of everyday - would be as satisfying, Derek thought, as any other wish he might have granted himself, if he could have. 

It was easy to escape, to slip past the guards. Derek had done it several times before with Laura, sneaking out to go to village parties. Laura liked watching the dances, eating the food and enjoying the local wines; Derek liked watching the people, doing and saying they pleased, holding hands and arguing - even if it did make him envious. 

Derek sometimes wished he was rebellious; rebellious, like the princes he used to read about - the ones in the story books his parents brought back from their travels. Derek knew it was best not to dwell on ridiculous fantasies, on happily ever afters- it was the kind of freedom he couldn’t afford to think about, or depress him - not if he wanted to make his family proud.

The gardens were extensive but the wall itself was a short walk and Derek couldn’t help but feel excited, never having explored this part of the palace before. 

Disappointment soon dampened his spirits, however.  

There was nothing extraordinary about the wall at all - it extended so far out, that Derek couldn’t even walk around it. It felt almost like a cage, or a prison. There wasn’t even a tree he could climb; nothing to help him see over to the other side, to where he knew the ocean was. There was nothing but a lake - black, dead, as the night sky. 

Derek had never been allowed near the ocean and up until now he had never considered why. What was so dangerous about it? Water couldn’t hurt him - not if he didn’t go in it - and even if he did, he was a strong swimmer. He lived his life in the pool, swimming lap after lap, every morning. To be able to swim in the ocean, to be granted a wish, he thought, would be nice; to be able to live in it and never look back. Glancing over his shoulder, to where the party was still ongoing, he longed to be Cinderella or Aladdin, so his wish might be granted.

This, of course, wasn’t a fairy tale and magic - as much as Derek had once believed in it - did not exist. There was no escape; no ocean large enough, no star big enough, to grant  _ him _ the freedom he desperately wanted. 

Sighing, Derek began to turn away, eyelids growing heavy, but at the sudden sound of a voice, he stopped. 

He couldn’t make out where the voice was coming from, but it seemed to be singing. At first, Derek thought it was a foreign tongue but as he listened closer, turning towards the voice, he could make out enough words to recognise the song was being sung in his own language. 

It was beautiful. 

He didn’t realise he was walking towards the lake before he was crouched down in front of it, hands poised just above the black surface. It wasn’t well lit, the moon the only source of light, and where at first Derek could see the wall, now he saw nothing but the water, beginning to glow, as though a fire had been lit underneath it. 

Derek’s breath hitched, mesmerised - not by the sight - but by the head that broke the surface. It wasn’t close enough for Derek to see, and he couldn’t tell if he was looking at an animal or a human, but the two amber eyes that shone out were  _ dazzling _ . He longed for who or what it was to come closer, that he might admire them better; perhaps...even touch?

“I won’t hurt you,” he called out, treading the water with his hand, hoping to beckon them -  it - forward. The creature tilted its head in response, a smile- although, Derek couldn’t be sure- playing on its face, before disappearing below the surface.

Surprising himself, Derek called out again, afraid he scared it off  but before he could mourn the loss, the creature showed itself again, its face now directly under his, looking up at him - staring.

Derek gasped.

It wasn’t a creature. It was a boy.

A  _ beautiful  _ boy.

His eyes - wide and brilliant - complimented pale skin scattered with moles, almost artistic in their placement; the soft, rosy mouth and upturned nose, Derek couldn't fail to be captivated by. It was the kind of nose Derek had always loathed; a snooty nose, as Cora would say - but on this boy, there was nothing snooty, or loathsome, about it. 

The logical part of Derek’s brain told him it was just a nose, that noses weren’t supposed to be attractive - that noses  _ weren’t  _ attractive - but the longer he looked, he had to disagree. In fact, Derek didn’t know which part boy’s face struck him most; every line, spot and curve entranced him, stirring something inside of him. It was scary and wonderful, and Derek couldn’t help the way his mouth dropped open. 

“Derek,” he whispered, desperate to reach out, to touch, recollecting himself only at the last moment. It would have been impolite to touch without asking, he reminded himself, and even if it hadn’t been, it would still be inappropriate. The boy was a stranger, after all.

A perfect, beautiful stranger. Derek smiled. 

The boy looked at him curiously, tilting his head this way and then that, before frowning. Derek blushed, wondering if he didn’t like what he saw. 

Derek had always been told he was handsome - he knew the way people looked at him, touched him sometimes, getting too close- but this boy wasn’t looking at him, he was assessing him- careful, calculating. It was unnerving,  _ refreshing _ , and eventually, the boy shook his head and smiled. It wasn’t an encouraging smile, not exactly. Derek didn’t know what it was, but it still made his stomach flutter.

“Derek,” he said again, hoping he could get a name in return this time, unconcerned by the fact the boy was still in his  _ lake.  _ Perhaps, he thought, he should demand an explanation, but he wasn’t Peter. Derek had never viewed their property as sacred ground, only fit for those who could “afford” to visit them. Derek didn’t care if the boy was from the village or a visiting kingdom. He didn’t care he was swimming, late at night, alone.

Swallowing, he tried to think of something else to say. He had always been shy, had been chastised many times for his inability to hold conversations, but tonight he wanted the universe - just this once - to grant him an exception; tonight, he wanted...well, he didn’t know what he wanted but he wanted  _ something.  _

To his frustration, however, he couldn’t think of anything and the boy didn’t answer him, continuing to stare at him, before sliding his hands out of the water and placing them beside his own. He smiled then, making Derek’s heart skip a beat. 

Derek barely had a moment to look down, to see what perfect hands looked like, before the boy was lifting himself out the water, leaning forward, and pressing his lips against his. 

He knew he should resist but Derek couldn’t help but give himself over to it, overwhelmed. He had never been kissed before, not by anyone, and the way the boy’s lips caressed his, gently at first, before claiming his mouth - hungry - until he was all Derek could taste, had him  _ aching _ . It was the kind of kiss he had never dared hope for, having resigned himself to the dreaming of kisses only political matches could bring. Those dreams always left Derek feeling cold and he shuddered, revelling in the warmth of the boy’s tongue, dipping into his mouth. 

Derek knew he wanted love, craved but would never get it, and even though he knew he shouldn’t, he let himself go - just this once - kissing back, pleased when he felt the cool touch of the boy’s fingers threading through his own.

It took Derek a moment to realise his body was moving, his head light with pleasure as his hands slid up, resting on naked shoulders, as he was pulled down. It was only when Derek’s head broke the water’s surface, he realised what was happening - he was being pulled  _ under  _ \- and pushing against the boy, flung himself back out of reach, breathing heavily- from fear or the kiss, he couldn’t tell.

“What-” he began to ask but the boy raised his hand, cutting him off, staring at Derek wide-eyed, a look of great surprise on his face, before vanishing into the lake.

It was then that Derek saw it; the golden, red tail where a pair of legs should have been.

***

Mermaids.

Merfolk?

Merfolk.

No matter how many times, or in how many different ways, Derek said it, the existence of... _ merfolk _ was hard to swallow.

Merfolk.

The next morning, he was certain it had been a dream but his shirt, still wet from the night before, dampened that theory. 

“Merfolk,” he whispered, walking back towards the window, still open, looking out. “ _ Merfolk.” _

Derek had never been the curious sort but now he knew, he needed to  _ know _ . He couldn’t let it go. He wanted to know every fact, every story, and after three days of trying to find something,  _ anything,  _ on merfolk in family library and coming up empty, he finally found himself in front of the one person’s door he trusted. At least, to give him answers. 

Deaton was an enigma, to the say the least. Derek didn’t know where he lived or who his family was. Derek didn’t even know if he had any friends. He knew nothing about him, except he was his personal tutor; had been, since Derek was five.

Derek wouldn’t call him a friend but he was the closest thing he had to one, the only person he had been able to turn to since his parents died. Laura and Cora preferred archery and riding to books but Deaton was widely read, and even though Derek had never been able to talk to him, the debates they had, the questions Deaton posed to Derek, were enough to sustain him. Enough to take the sting of loneliness away when Laura or Cora were too busy, which was often. 

Sometimes, when he was particularly excited about a book, Derek talked to the paintings on the walls. The ones closest to his parents’ bedroom were his favourites and he often read to them, gushing over passages and grinning over characters. Other times, when the paintings were not enough, he tried to talk to the servants but they often avoided him, knowing Peter did not like Derek conversing with “the help”. It made Derek’s blood boil, how his Uncle spoke, but there was nothing he could do. Not without getting them into trouble.  

“Merfolk,” Derek said, trying to keep his voice level, taking his usual seat in Deaton’s study. “I want to learn about merfolk.”

Deaton paused for a moment, raising his eyebrows, giving Derek an almost quizzical look before leaning forward, resting his chin on his knuckles. “What do you want to know?” 

Derek blinked, having expected resistance, but when he opened his mouth to speak nothing came out. What  _ did _ he want to know? What was he supposed to ask, without revealing what he saw? Averting his gaze, he shifted uncomfortably.

Deaton sighed. “You went down to the wall, didn’t you.” It wasn’t a question and Derek nodded, knowing it was never wise to lie to Deaton. Even Laura found it impossible to lie to him and Laura was an excellent politician - she could lie her way out of anything. 

“You shouldn’t have done that,” Deaton continued. He was angry, arms folded, and Derek swallowed, unused to seeing Deaton anything other than passive. “Did you see him?”

The question took Derek by surprise. “The boy, you mean?” he asked, biting his lip. Merman. “Yes.”

“Did you speak with him?”

“No,” Derek said, shaking his head, silently praying Deaton didn’t ask him anything else. He wanted to learn but it didn’t seem like a good idea now; to share the details of what had happened with Deaton seemed...like a betrayal, somehow. If he concentrated hard enough, Derek could still feel the boy’s lips on his, even now, making them tingle. He knew it was just his imagination but he couldn’t help but press down on them, letting the memory wash over him again and again. It was like a drug.

“Did you go near him?” 

Derek swallowed again, watching Deaton’s eyes narrow, fearful. He shouldn’t have come here. “A little?”

“I’m surprised you’re still alive.”

Derek frowned, remembering how he had been pulled under the water. “What do you mean?”

“You’re telling me he  _ didn’t _ try to drown you? Killing is not part of a merperson’s nature, it  _ is  _ their nature, Derek.”

Derek flinched. So,  _ that’s  _ what the kiss had been about, after all. He tried not to let the words depress him, but it was almost impossible. The confirmation stung. He had hoped-

He didn’t know what he had hoped.

“But he did try to drown me,” he said, after a moment. “He had my face under the water but I pulled back. He…left.” 

Derek couldn’t help but picture the tail again, a warm sensation curling in his stomach as he imagined being able to touch it; to feel the golds and reds under his skin. The thought alone felt dangerous, exhilarating, and Derek tried to push it out of his mind.  

“He left,” Deaton repeated, dryly. “That’s not - that not possible.”

Derek shrugged. “That’s what happened.”

Minutes passed, before Deaton finally turned his back to him. “Do not go back to that wall.”

“But-”

“No!” Deaton yelled.

“Professor?” Derek had never seen him this upset, not even when Cora had defaced six of his original, prized, manuscripts on her sixth birthday. They had been hundreds of years old - Deaton hadn’t even batted an eyelash. 

“Promise me, Derek.”

“Professor, I don’t under-”

“ _ Derek. _ ”

“Okay.” 

Raising his hands, Derek slid from his chair, running for the door as Deaton swung back around to stare at him like  _ he _ was the merman. 

***

Derek had no intention of going back to the wall, fearing Deaton’s reaction and what it meant, but as the days stretched on he was overcome by restlessness, unable to sleep, ignoring his lessons- even his books couldn’t hold his interest for long.  

Putting down his copy of  _ Pride and Prejudice,  _ he was tempted to break the rules again when the singing started, floating through his window, pulling him towards it. 

He was more than tempted.

Getting up, Derek headed straight for the door, captivated. The song was a whisper in his ears now, only loud enough for him to hear, and while the rational part of his brain told him to turn back - that maybe the reason he had been forbidden to visit the wall all these years  _ was _ for his own protection - he didn’t want to listen to it. 

It was no effort to sneak out again, as nervous as he was. The boy was already there, at the lakes edge, watching him. Derek watched back, entranced, as the boy’s mouth still moved in song, so quietly Derek barely caught the final notes before he stopped. 

The boy smiled up at him, a look of confusion crossing his face when Derek sat down in front of him. 

“Are you not afraid I might pull you in?” he asked. His speaking voice was different from his his singing voice, lower, for a few moments, Derek was at a loss for what to answer. It wasn’t uncommon for him to remain silent; he was used to it, comfortable, but this time, he wanted to reply. It was a strange feeling but one Derek liked. It wasn’t often he felt liberated, especially not in front of another person.

“You didn’t last time,” he finally replied.

“Yes,” the boy said, his brow furrowing further. “I didn’t.” 

Despite his beauty, Derek couldn’t help but notice how stern his face looked, how haunted it was - even when smiling - but on the last word the boy’s face softened and he laughed. It was a rich sound but real, completely different than how Derek imagined he might laugh- how a merman might laugh. Derek had never had a favourite sound but he quickly decided that could be - was - it. 

“Thank you,” the boy said. 

Derek blinked, frowning slightly. “For what? I didn’t do anything.”

“That’s the point,” the boy answered. “My family…they-” He sighed, looking away, and Derek tried not to smile as a creature, supposedly so dangerous and deadly, started to stumble with his own words. “We, you know,  _ kill _ . It’s...in our nature. It’s not…it’s not something we  _ mean _ to do, I want you to know that.” He scratched the back of his neck, cheeks colouring slightly. Derek found it utterly charming. 

“Then why do you do it?”

The boy looked down. “I’m not really...sure? Show us someone that appeals to us and we just try to take them….home, I guess.”

Derek raised an eyebrow, ignoring the fact he a part of him was trying to figure out of he was just described as  _ appealing _ . His heart did definitely not swoop at the thought he might have been. 

“Home, as in…?” He nodded towards the wall, where the ocean was. How did the boy even get in here? Did he swim through? Derek knew if he lived in the ocean, here is the last place he would come. The garden, while beautiful, was dark and lifeless. Even the trees provided little beauty.

“Exactly,” the boy said, nodding. “It’s like, in that one moment, we can’t remember that they- you- can’t come with us.” He sighed. “And then they drown.”

Derek laughed, even though he knew he shouldn’t, and the boy narrowed his eyes at him in return. 

“It’s not funny.”

“I know.”

“When I was little, there was a net and I…my family…they couldn’t...” 

Derek’s stomach sank, the smile wiped from his face. “You…you got taken?”

“I was brought here,” the boy replied, eyes losing their bright glow, darkening, if only for a second. Derek felt a shiver run through him. “It gets lonely sometimes and you were so close and -” His lip trembled slightly and he turned away. Derek winced, watching as his tail rose and fell, like the boy was trying to calm himself down; he wanted to reach out, to comfort him, stepping forward despite himself, the lake making him nervous. 

_ He would have drowned you. _

Despite what people thought, Derek was a tactile person. Or, at least, he wanted to be. He often fantasised what it must be like, to be comfortable enough with someone to touch them, to let them touch you without feeling awkward or stressed. Derek didn’t know why a merman, of all people, made him feel comfortable. Especially because he felt no pull towards him now - not as he had that night. He wasn’t overwhelmed, his head clear.

At least, as clear as it could be. He’d never felt this way before.   

“I was an easy catch,” the boy continued, twisting. “I always disobeyed, never stayed put. That’s how I ended up in here, I guess.” He turned his back to Derek, looking at the wall. “I can’t escape but I can hear my family calling to me, sometimes. They tell me stories, tell me how much they love me. They try to keep me company...but it’s still pretty lonely. They can never stay for long. Some days they can’t visit at all.”

Derek swallowed. “Is there anything I can do?” he asked. “Maybe if I told my Uncle-”

The boy shook his head. “No, please don’t. He would kill me. You’re the prince, right? You shouldn't be here. I’m a threat to you.” He smiled, like what he said was funny, but the smile slipped away too easily and Derek felt his stomach lurch, remembering how Deaton had reacted. He knew the boy wouldn’t stand a chance, not if his Uncle found out. Up until now, his family had let him live. Derek couldn’t fathom why but he was glad of it. Maybe his Uncle was scared of the boy, Deaton certainly was. Or, perhaps whoever captured him had once worked here, bringing the boy into the grounds without his family’s permission. Derek stilled, remembering the day Chris Argent was exiled from the Kingdom, and wondered. He had been his mother’s favourite hunter. Had he-

“This might not be much of an existence,” the boy interrupted Derek’s thoughts, “but I like it. Existing.” He averted his gaze but swam closer, offering a shy smile. Derek had the feeling there was another part to the story but he knew better than to ask; he hated it when people pried, he knew when to keep his mouth shut. 

“I’m sorry,” he whispered instead, uncertain what else to say, wondering how long the boy had gone without seeing a face, without conversation. Could he talk back to his family? Could he tell them how much he missed them?

“You’re the first human I’ve seen since that day,” the boy said, reading his mind. “When I saw you, I was overwhelmed. I don’t have….another excuse.” He ducked his head. “I knew there was no home to take you to, I  _ knew _ , but I wanted - I wanted someone to talk to so  _ badly _ .” He winced, swimming closer again, until he was under Derek, looking up at him. “I’m sorry for the kiss. I- I didn’t mean to do it. Honestly. I couldn’t help it. I swear.”

“No?” Derek whispered, his cheeks heating up at the memory. 

The boy shook his head. “I think that’s what broke it,” he said, confused. “The enchantment, I mean. If you want to call it that. Despite the stories, my people have heard your kind tell, we don’t give the kiss of death, we just drown people.”

“Charming,” Derek deadpanned, desperate to make the boy smile. After a moment, he was rewarded with one - a genuine one. It was an odd smile, but beautiful - rare, Derek thought, and he smiled in return, pleased. 

“So, uh,  _ again _ , sorry about the kiss but you’re in no danger from me now. No killing urges here. Merman’s honour. I won’t even splash you!”

Derek laughed, found himself saying, “I like you.”

“You do?” 

Derek nodded. “I’d like you even more if I could call you by your name.”

“Stiles,” the boy answered immediately, face lighting up.

_ Stiles _ ? “Is that some kind of weird mer-name?”

“It’s my nickname,” Stiles glowered, eye growing dark again. “My real one is too hard to pronounce.”

“Merfolk have  _ nicknames _ ?” Derek’s eyes wide, biting the inside of his cheek. 

“Yes,” Stiles huffed, folding his arms and pouting - the very picture of a petulant child. Derek tried his best not to find it adorable. “We’re not all that different from you.”

“Apart from the drowning thing.”

Stiles rolled his eyes. “Apart from the drowning thing.” His face softened and he inched closer again, peering up at Derek, as though trying to figure him out. Derek could smell the sea water on him, the way it clung to his skin like a heavy perfume and he breathed it in, coughing, looking away, when Stiles smiled, noticing. 

“Do you want to see my tail?” Stiles asked a moment later; it came out in a rushed breath, like he was embarrassed to ask and Derek frowned, glancing down into the lake. It was still black, almost solid - he couldn’t see a thing. 

“Do I have to get in the water?” he asked, warily. 

Stiles’ eyes widened. “Don’t worry, I’m not going to hit you over the head with it. I just,” he bit his lip, “want to see if you like it.”

Derek nodded, torn by amusement and curiosity, watching as Stiles dived under the water. It wasn’t a second before Stiles’ tail made an appearance beside him, flopping somewhat awkwardly onto the stones, moving restlessly like a fish, literally, out of water. 

Derek grinned. 

He had always assumed merfolk were graceful creatures; the creatures from the books he read as a kid, but Stiles was either the exception or the stories were wrong. Stiles looked graceful but he reminded Derek of a baby deer; his eyes alone were like a woodland animal’s, and while Stiles’ hands were still as hypnotic, as smooth, as Derek remembered them, Stiles’ tail was...wriggly, like a puppy or an overexcited baby. 

Derek smiled. However, the moment he reached out to touch it, it stilled completely and Derek took a moment to appreciate it. It really  _ was  _ beautiful; shades of red and gold, ranging from ruby red to sparkling yellow, glistened, taking his breath away. He couldn’t help but reach out and caress the scales, bumpy but not rough, caught between fascination and awe.

When he stopped, Stiles resurfaced; his cheeks were coloured a deep pink.

Derek frowned. “Did I do something-” 

“I didn’t think you’d touch it,” Stiles said, ducking his head shyly. “It’s kind of a….sensitive area.”

“Oh!” Derek gasped, feeling his own cheeks heat up in embarrassment. “I didn’t mean to-”

“It’s fine,” Stiles cut him off, biting his lip again, drawing Derek’s gaze to his mouth, wondering if Stiles often bit his lip, or whether he only did it when he was nervous. “But, did you…uh, like it?”

There seemed to be a lot riding on Derek’s answer - if the look in Stiles’ eyes was anything to go by - and he knew he couldn’t take too long to reply. 

“It’s the most beautiful thing I’ve ever seen,” he said, honestly. Maybe a little too honestly. “I can’t think of anything, painting or sculpture, as beautiful.” 

It might have been Derek’s imagination but he could have sworn Stiles’ puffed his chest out a little. 

His eyes must have wandered down, tracking the thought, because when Stiles caught him looking he disappeared again, diving below the surface.

The fact he didn’t say goodbye gave Derek the justification he needed to return tomorrow night.

After all, it would have been rude not to.

***

“What do you do?” Stiles asked. “As a Prince, I mean.”

Derek had known Stiles for five months and if there was one thing he had learned, it was that Stiles was the curious sort; he wanted to know  _ everything _ , and while Derek had always hating answering questions, he was happy to oblige Stiles. He often snuck books out from the library to read to him, often reading for hours at a time.  He had never been happier, even when holed up in his bedroom alone with nothing but a book and a glass of milk.

Stiles was particularly fascinated by the male anatomy - circumcision, in particular, struck him with a sort of strange delight and Derek found it difficult not to stumble over his words as he read to him from one of his father’s old medical journals, as Stiles leaned in close to look at the pictures. In return, Stiles taught Derek the constellations. At least, the constellations his mom had taught him, over the years. He was a fast learner and his mind was even faster, remembering everything Derek read to him, everything his mom taught him, asking new questions every day. It fascinated Derek to no end, watching as Stiles’ mind worked.

Stiles also liked to listen to Derek read from his favourite books, making him stay late, so Derek might finish another chapter.  _ I need to know if Elizabeth marries Darcy, Derek! You can’t leave me like this! I’ll splash you if you try!  _ It was Derek’s favourite way to spend time with Stiles; not just because Stiles was the first person to actually  _ grin _ when Derek talked - especially about books - but because Stiles listened. He listened to everything, never giving Derek the impression there was somewhere else he wanted to be. He didn’t want to know what Derek had learned, like Deaton did; nor did he roll his eyes, like Laura and Cora did, however fondly. Stiles wanted to know what  _ he  _ thought, only rolling his eyes when Derek held  _ back.  _ It was new, and Derek often didn’t know how to take it, not used to Stiles’ particular brand of attention. 

“My sister, Laura, will be Queen someday,” Derek said, tucking into the bread and cheese he had sneaked from the kitchen. “She’s not ready yet, but she will be.”  Stiles didn’t need to eat but the smell of the bread appealed to him and he picked a slice up, as he did every time Derek brought bread with him, sniffing at it while Derek ate, turning it over in his hands.  

“As the youngest, it’s my sister Cora’s job to be the people’s voice,” he continued. “She makes sure they are happy, talks to them about new and old legislations, talks to my Uncle about changes they wish to see. That sort of thing.” He smiled. “She’s really good at it and it makes her happy.” He shrugged. “I think she likes living away from the palace, more than anything. I sometimes see her with a redheaded girl from one of the villages, holding hands.” He smiled wistfully. “Cora can marry freely,” he added, turning his face away. 

“And you?” Stiles asked, steering him back to the original question. Derek shrugged, breath hitching when Stiles’ hand brushed over his, soothing. It always surprised him how cold Stiles’ skin was but how warm it always made him feel. 

“As the middle child, it’s my duty to keep the peace between our...neighbouring kingdoms.”

Stiles tilted his head, making Derek smile, despite himself. He used to find it eerie, the way Stiles did that. Now he just found it endearing. “How do you do that?”

Derek frowned, gut clenching. He had never talked to anyone about it before- whenever he had tried, guilt always got the better of him - but he knew Stiles would listen, without judgement, without opinion. He had tried to talk to Peter about it, once, but he had only been met with a disappointed look; one that said  _ selfish.  _ Derek had never brought the subject up again.

“I marry,” he whispered, eventually.

“Oh.” Stiles lowered his gaze, hiding his face. “Are they very beautiful?”

“I wouldn’t know, I haven’t met them yet. They might not even be born.” 

Stiles’ mouth fell open and he wrinkled his nose. Derek nodded. His parents had had a large age gap between them, but they had been lucky enough to fall in love, a few years after they got married. Derek couldn’t imagine being married to someone twenty years his junior - senior, maybe - and not love them- or, at least, not being able to  _ learn _ to love them. It made him depressed, picturing it.

“Do you have mistresses?” Stiles asked, interrupting the thought.

Derek smiled, narrowing his eyes. “Are you jealous?” 

“What?” Stiles spluttered, splashing a little. Derek's smile widened. “Of course not, I’m just thinking of your personal  _ needs _ and-” he lowered his eyes. “Okay, fine. Maybe I’m...a  _ little  _ jealous? Or, you know, a lot.” 

The confession was barely audible, a blush painted on Stiles’ cheeks to accompany it, and before Derek knew what he was doing - blushing himself-  he shifted, leaning down to kiss him. At first, he missed, grazing Stiles’ jaw but leaning in closer, pressed his lips softly against cold ones.

Stiles gasped when Derek bit down, over excited, but didn’t pull away, pushing himself out of the water and wrapping his arms around Derek’s neck, trusting Derek to hold him. It was their second kiss but it felt like their first, the sound of Stiles’ tail below them - splashing excitedly - making Derek giddy, grinning foolishly into Stiles’ mouth. It made it almost impossible to continue but Stiles, fast as ever, slid his tongue over Derek's, sucking on it, turning the smile into a moan.

Derek had always hated his size, his muscles often attracting the sort of attention he didn’t want. People always thought it was okay to touch him, to prod and poke while they complimented him, but right now, right here, he couldn’t be more grateful for his strength, wrapping his arms around Stiles’ waist, holding him up easily, close -  _ tight  _ \- allowing him to explore the mouth against his without distraction or strain, biting down on Stiles’ lip again, this time with intent; tugging on it, pleased when it made Stiles shiver.

Relaxing his hold on Derek’s neck, working a hand into his hair, Stiles turned the kiss from gentle to demanding, murmuring words Derek couldn't understand, pulling on Derek's hair until he was forced to pull back, gasping for breath. Stiles, while not composed - definitely not composed, Derek noted a little smugly- merely hummed when they finally broke apart, his breath control frustratingly, annoyingly impeccable. How was that  _ fair _ ? His eyes, however, were a darker shade of amber than usual, glowing slightly, and Derek couldn’t help but feel...triumphant at the sight. He did that.  _ Him.  _

“Thank you,” he whispered, moving to lower Stiles back down into the water, a little awkwardly, not wanting to let go. “I never thought I’d get to do that…with someone like you.”

“A merman?” Stiles quirked an eyebrow. It was a look Derek wasn’t sure was teasing or not and he blinked, realising- realising there were still so many things he had to learn about Stiles. He wanted to know what Stiles looked like when he woke up in the morning, if he had a favourite word or colour. He wanted to be able to tell the difference between a teasing look and a dumbfounded one. He wanted to spend a life time learning and it scared him, how much that thought didn't scare him- that, for the first time, there was a future that didn't fill him with dread but the opposite.

“No,” he said, shaking his head, swallowing. “With someone that makes me feel…I don’t know, achy?”

“Achy,” Stiles repeated, frowning. “Is- is that a good thing?”

Derek smiled, cheeks heating up, wondering if there would ever come a time when he didn't blush around this boy. “Very good,” he whispered, shaking his head as he watched Stiles’ face relax in relief, like there had ever been a  _ possibility  _ for it to be bad. 

“You, uh, make me feel achy too.”

Derek laughed, biting his lip. The word suited Stiles, somehow; it made Derek think of something he had been curious about for a while now.

“Do you- do you ever do anything beyond kissing?” 

Stiles blinked. 

“Not that I’m asking for, uh, you know,” Derek quickly amended. “It’s just...how are you...born? Do you lay eggs? Does it take, um, more than...one of you?”

“Sex,” Stiles laughed, eyes widening. “You’re talking about sex.”

“You know about sex?” Derek asked, stupidly. Stiles rolled his eyes.

“Of course I do!” he cried. “ _ Well _ , Scott, he was - is- my best friend. He tells me about...things like that. I know it's pretty awkward for him, he’s pretty shy, but he does it anyway, says I need to know ‘the important stuff’.” He smiled, shaking his head. “I’ve never had it with another person, obviously, but I can...please myself, when I want to.” He added the last part somewhat hesitantly, blushing, sneaking a glance at Derek’s face.

Derek swallowed, eyes drawn to the water, where Stiles’ tail was. Derek remembered Stiles telling him it was sensitive and, suddenly, he wanted to know  _ how _ sensitive.

“Have I piqued your interest?” Stiles asked, waggling his eyebrows, although clearly nervous, eyes flitting between Derek and his hands. 

“Yes,” Derek answered, truthfully. 

Stiles sucked in a breath, obviously not expecting that answer. “You-” he gaped. “ _ Really _ ?”

Derek nodded, and Stiles lifted his arms out of the water. “Help me out?” 

Derek didn’t hesitate, shifting onto his knees, pulling Stiles out. He was just as light as he had been before, which surprised Derek because Stiles’ tail wasn’t small. He was certain, if Stiles wanted, he could injure him with it. Severely. 

“It’s kind of weird,” Stiles said, wriggling a little, cautiously laying back as Derek set him down, putting his arms behind his head. “Land. It's so...dry. I don’t know how you stand it.”

“You get used to it,” Derek replied, suppressing a smile, unable to come up with something wittier, because Stiles’ tail...was Stiles’  _ tail _ .  Despite having seen it several times, usually Stiles was showing off, doing a trick or waving goodbye, Derek could never get used to its beauty. He doubted he ever would.

“You can touch it, if you want,” Stiles said, biting his lip.

Derek licked his lips, nervous. “Okay”, he whispered, reaching out, stroking over the scales gently. Stiles’ eyes fluttered shut. “Do you like that?” 

“Very much,” Stiles answered, nodding. “Keep going.”

“Demanding,” Derek teased, sucking in a breath when Stiles didn’t reply, the upper half of his body arching up as he began stroking him in earnest, touching every part of Stiles’ tail he could reach, starting at the top and working his way to the bottom. Derek had never paid attention to Stiles’ fins before but when his fingers made contact with them...he swallowed, eager, curious, when Stiles made a strangled sound and they became...wet. Well,  _ wetter.  _ He almost drew back but Stiles’ hand reached out, reassuring him.

“Please,” he whispered, trying to sit up but his body tensed, flopping back down, mouth open as Derek continued, taking one fin between his fingers and teasing it. Derek didn’t know if he was more fascinated or captivated, watching as Stiles began shake; all he knew was that Stiles was beautiful - everything he had ever imagined - and leaning down, took the other fin in his mouth. 

Stiles let out a surprised yelp and Derek grinned, watching as his tail turning a deep shade of red, warming under him. Curious, Derek gently started to suck, flushing when Stiles moaned, loud and unreserved. He tasted good, if slightly odd - a little like, well, Derek didn’t want to say  _ fish _ but…

“ _ Derek _ ,” Stiles gasped, arms moving, twisting above his head. “I can’t -  _ wait. _ ” He exhaled shakily and Derek smiled, pleased, as he continued to explore him. It made Derek feel powerful, alive, and when Stiles’ tail started moving too, restless, Derek pinned it down with both hands, breathless,  _ excited _ . 

“You’re so beautiful.” 

“Derek,” Stiles said again, barely a whisper this time. “Derek, please, I- you need to  _ wait  _ because...”

Derek stilled, looking up, wide-eyed. “Are you going to-”

“ _ Yes. _ ”

Stiles shook as he came, cursing in a language Derek couldn’t understand. 

“Dolphin,” Stiles supplies, smiling goofily, after a moment. 

“Dolphin?” Derek blinked and Stiles nodded. 

“You could say it’s my first language, if you were going to get technical about it.” 

_ Dolphin.  _ Derek blinked again. “Would you teach me?”

Stiles laughed. “If you wanted.”

“Are you alright?” 

Stiles gave him a thumbs up and Derek crawled up his body, kissing him as he did. 

Stiles looked blissed out when he reached his face, his eyes even darker than before; they almost looked frightening, haunted in a way that reminded Derek of the first time he saw him but he couldn’t find it in him to be scared, mesmerised by the smile on Stiles’ face. A smile he put there. Derek didn’t know it was possible to feel so happy, just from making someone smile. Especially someone like Stiles.

“You’re welcome,” he said, only to be met a glare.

“If you’re going to be smug, you can forget  _ all about _ me returning the favour. You know, when I regain the feeling in my tail, that is.”

Derek grinned. “I can take care of myself later.”

Stiles cracked open one eye. “No, let me take care of you. Just...give me a few moments. To nap.” He sighed, smiling, opening his arms for Derek to crawl into. 

“I thought you once told me merpeople aren’t snugglers.”

“We’re not.”

“Then why-”

“Shh, don’t question it. Just...just come here, Derek.” Stiles held out his arms further and Derek didn’t hesitate, burying his face in Stiles’ neck and breathing deeply, letting himself be held. “This is nice.”

“Yeah,” Derek whispered, heart beginning to race. “It is. More than nice.”

“Maybe we should snuggle more often. You can read to me.”

_ Yeah,  _ Derek thought, burying closer, blushing when Stiles laughed. 

“What are you thinking?”

_ That I’m falling for you.  _ “How lovely you look when you come.”

They didn’t snuggle for long after that, Stiles rolling them over and kissing Derek until he couldn’t think about anything other than how impossible it was to stop smiling. 

***

“Can I ask you something?” Stiles asked. He sounded scared and Derek instantly put the book he was reading from down. Stiles didn’t usually interrupt him when he read, especially when it was on a subject he was interested in. 

Greek mythology was something Stiles had become completely enamoured by recently. He particularly liked the stories of the sirens and water nymphs; or, at least, he was curious about them.  _ Do all people think we’re killers? _

“Anything,” Derek replied, trying not to frown.  He was happy, for the first time in years he was actually  _ happy _ . It made him feel guilty, to think Stiles could make him happy where his family couldn’t but Stiles wasn’t just  _ Stiles  _ anymore. He was...he was  _ something.  _ He didn’t want this to end. Not yet. Not ever.

“Can I-” Stiles bit his lip, eyes sweeping over Derek’s face. “Can I see you?”

Derek blinked, confused. “See me?” 

“Yes,” Stiles whispered, lowering his eyes shyly, looking at-

_ Oh. _

“Oh,” Derek’s eyes widened, following Stiles’ gaze. “See...me.” 

The thought of Stiles looking at him -  _ just  _ looking - made him nervous, scared, but the thought of refusing...he swallowed. He didn’t want to say no. 

“I’ve never…” Stiles started to babble, in the way he sometimes did. It made Derek relax and he smiled. Stiles had a habit of making him do that, lately more than ever. “I just...want to see what’s...there. You don’t have to. I’ve just been, you know,  _ curious _ ever since….when you were…with me...and something twitched…there.” He nodded in the direction of Derek’s crotch again, blushing, and Derek bit back a laugh. 

The fact Stiles was _embarrassed_ made him relax completely; made him _fond._ Fonder, if possible. Stiles’ insatiable curiosity wasn’t something Derek was in the habit of resisting. Last week, he had spent hours tracking down a book on unicorns - had gone into one of the neighbouring villages to get it - just because Stiles happened to mention he would like to see a picture of one. To say Derek loved satisfying Stiles’ curiosity, to get to be the one to _do that,_ to put a smile on his face, was an understatement. 

A gross understatement. 

“I…sorry,” Stiles whispered, looking down again, apparently taking Derek’s silence as rejection. Derek watched as he began to slip away, the blush on his cheeks turning his skin blotchy. It was adorable.

“No, wait, I-” Derek took a deep breath, closing his eyes and fumbling, pushing his pants down his legs. He wasn’t wearing any underwear - he had been in such a rush to get out, to see Stiles- and while he knew his cheeks were probably red, he was too distracted by the look on Stiles’ face to care. 

“Can I touch it - I mean, you?” Stiles asked, mouth open, swimming back towards him.

Derek nodded, smiling, sitting down at the edge of the lake. He couldn’t kneel, the position was too far away for Stiles to reach him, but sitting with his legs splayed - he swallowed, blushing at the thought.  “I’m - I’m gonna-” he said instead, slowly lowering his legs into the water, so he was sitting right on the edge.

Stiles sucked in a breath. “You trust me that much,” he whispered, “not to pull you under?” 

“Yes,” Derek said, and Stiles’ eyes widened. It had almost been a year since Derek had first seen him, a year since he had first spoken to him. Five months, to the date, since he realised he would never love anyone else; at least, not in the same way. “I trust you.”

Stiles smiled, looking down for a moment, inching closer again. “Thank you,” he whispered, barely audible. “I…I never expected-” 

Derek wasn’t fully hard but when Stiles reached out, wrapping his fingers around him, his body didn’t fail to respond. It felt good,  _ more _ than good, to have someone else touching him. To have  _ Stiles _ touching him. It was nothing like his own fingers and swaying forward, trying to bite back a moan, he gasped, desperate to find purchase on something. All he could find were Stiles’ shoulders.

Stiles didn’t seem to mind, however, head briefly tilting to the side to nuzzle at Derek’s hand, placing a wet kiss there. It was strangely intimate, more intimate than Stiles’ fingers wrapped around him, and Derek bit his lip, whimpering slightly when Stiles flicked his wrist, moving his other hand, exploring a little lower. Derek had never touched himself there and he made a half-choked sound, thighs trembling slightly at the new sensation.

The look in Stiles’ face turned from fascinated to admiring and Derek tried to bite back a laugh, self-conscious, except it only made matters worse, knowing that the sight of him could make Stiles look like  _ that-  _ with awe - and he laughed anyway. It was a ridiculous laugh, high-pitched and a little strangled, but Stiles didn’t tease him on it, like he ordinarily would have done.  

“Is this good?” he asked instead, fingers sliding down, careful. Derek nodded, unable to reply, hips stuttering as he watched Stiles bring his fingers to his lips and - fuck - taste him. He closed his eyes, willing himself not to come yet. He could last longer than this. He  _ would  _ last longer.

“You taste good,” Stiles whispered, “like the sea.” He smiled when Derek looked at him again, eyes going wistful for a moment, before returning his attention to him. “Can I keep going? Would you - would you like that?”

“Please,” Derek said, swaying forward again, trying to keep his legs from kicking out. He was achingly hard now; red, he imagined. It would have been embarrassing, except no one had ever touched him like this. It wasn’t his fault he was already desperate to come, especially not with Stiles.

“Thank you,” Stiles said, politely. 

Derek grinned, shaking his head. “I should be the one thanking you.” 

“Maybe,” Stiles teased, getting a hand around him again, exploring, drawing patterns with light touches. It was amazing, just to watch; amazing, but excruciatingly slow and Derek pushed forward.

“More,” he gasped. “Please, Stiles, _ more.  _ I need…” He whimpered, unsure. He didn’t know what he needed.  _ You,  _ he thought.  _ I need you.  _

Derek had never teased himself before, too afraid someone might walk in on him - his door hadn’t had a lock since his parents died - and the thought of Stiles, stripping him hard and fast, like he usually did to himself, made him whimper pathetically. He didn’t know if he would be able to take it, he was already feeling over-sensitive, but the pace Stiles was setting was also...too much, not enough. Clutching Stiles tighter, he whimpered again, feeling torn. 

“I’d like to taste you again,” Stiles said. Derek panted in response, earning a chuckle before - oh god, that was a mouth. That was a warm, wet,  _ skilled  _ mouth. Briefly, Derek wondered if it was a merman thing - that tight, perfect pressure - but as he watched pink, plush lips wrap themselves around him, taking him in and sucking him down until they were - yes,  _ please  _ \- right at the base, Derek decided it was a Stiles thing. He always did pick up on things quickly, and why should sex be the exception? 

“Stiles,” he gasped, stomach clenching. “I’m going to…you need to pull off or I’m…I’m...ah!” 

Stiles didn’t heed him, flicking out his tongue, encouraging him. “I want you to,” he said, making his skin tingle, his head dizzy and- 

\- and that was it. 

It almost hurt to come, shouting out as Stiles swallowed, soothing him with gentle hands, rubbing circles into his skin. Again, it’s oddly intimate, overwhelmingly reassuring  - that touch - and Derek exhaled shakily, collapsing on to the stones as Stiles pulled off, panting heavily. It was only when he felt Stiles’ hands running up his thighs, trying to draw his attention, did he force himself to sit back up, open his eyes.

Stiles’ mouth was- Derek swallowed. It was puffy and red and _wet,_ and the next thing he knew, he was in the water, sliding his arms around Stiles’ neck and kissing him. There was no stopping himself; he needed to, needed _this,_ and his future - be what it may - would never take it from him. If all he got, in years to come, was the memory of this, right here, right now, Derek knew he’d always be grateful. Sad, but grateful. 

Stiles made a surprised sound, a little  _ oomph,  _ hands clutching at Derek’s waist like he was terrified he might drown, trying to hold him up. Derek shook his head, deepening the kiss, unable to pull back, to tell Stiles he could swim - that he didn’t need to hold him. He liked the feeling of Stiles’ hands on him - loved it - holding him protectively. He felt almost ashamed of how wonderful it made him feel but no one had ever held him as close as Stiles was holding him now, not even his parents. He couldn’t help but bask in it. 

It was Stiles who eventually broke the kiss, pulling back just enough for Derek to see amber eyes, burning into his. They were brighter than normal, luminescent, and Derek felt those first waves of entrancement wash over him again, reminding him of the first night he saw Stiles, but this time they held no power. This time he felt different - a connection. Derek knew he would never be able to describe it but it was there, clutching him, binding him to Stiles in a way that made him feel safe, content. 

“I need to ask you something,” Stiles whispered, exhaling shakily, “but first...I need to know if you trust me.” 

“I think you know I do,” Derek replied, bringing one hand up to cup Stiles’ face. And that it was it, wasn’t it. Trust. Derek trusted Stiles more than he trusted anyone. Not because he trusted Stiles with his life, as he trusted Laura, but because he trusted Stiles with himself. He trusted Stiles to understand him, to pick up the parts of him he found difficult to hold on to; to keep those pieces safe when Derek couldn’t look at them. 

Stiles leaned into the touch but it was hesitant, sad, and he closed his eyes. “Do you trust me enough to drown you?” 

Derek stilled. “Say that again.” 

Stiles laughed, nervous, and his ars began shaking. “If promised you you would come to no harm, would you let me drown you?”

Fear gripped Derek momentarily, logic making his heart race, but he knew his answer - he was sure of it. 

“I’d let you.”

Stiles’ body tensed, as though surprised. “I hoped-” he started to say, eyes wide, “but I didn’t think - you’d really let me?” 

Derek frowned, not understanding, and he pulled Stiles closer, kissing his forehead. “Tell me what’s wrong,” he whispered.

“You mean a great deal to me,” Stiles said, instead of answering. 

Derek didn’t know how to respond to that. Instead, he looked at him, smiling shyly when Stiles looked back, little touches here and there, before Stiles blinked and the spell was broken. 

“Derek,” he whispered. “What - what if I told you there was another part to my story? The one I told you, that second night?”

“I’d say you can tell me anything.”

Stiles sighed, relieved, and Derek frowned, curiosity and the urge to hold Stiles, to bring him closer, warring inside him. He knew Stiles needed space when he talked but Derek was afraid to let go, scared he’d never get another chance to hold him again if he did.

“Say that there is a legend,” Stiles whispered, “about the union between a merman with _eyes that burned as bright as fire,”_ he rolled his eyes, “and a Prince _whose attention could not be held_ _by anyone_. Say, a man prophesied this legend, prophesied that the merman and the Prince would meet and fall in love. Say, such a union, between land and sea, was possible and this scared the man. Say, he watched over the Prince all his life, doing everything he could to prevent the Prince finding out about the merman.

“Say, the merman knows this man, knows him well. Say...the man tried to kill the merman when he was young. Continued to try, over and over, but could never kill him, because the legend, so they say, protects him.” Stiles exhaled shakily and Derek felt his tail wrap around his legs, not holding him but holding  _ on  _ to him, his hands beginning to tremble.

“Say, the merman never believed in this legend, that he thought it was a lie, a story told to him by his captor, to justify why he was taken and forced to live in...in here. What- what would you say?” 

Derek blinked, realisation slapping him across the face as he began to understand what Stiles was trying to say. 

“Did - did the man look like me?” he asked, thinking of his Uncle. 

Stiles hesitated, before nodding and then shaking his head at the same time. “One of them did. The other one - he was the one who tries to...who  _ tried _ to hurt me. He gave up some time ago. When your parents died, I think. There were bells the night he stopped.” 

Derek felt sick, thinking back; conversations, warnings...watching as they all began to fall into place. They weren’t Stiles prisoner, afraid of his magic, of who he was. Stiles was theirs and theirs only.  _ Stay away from the wall.  _ “What did he look like?”

Stiles bit his lip, reluctant to answer. “Bald, darker skin…scary.”

“Deaton,” Derek whispered.

Deaton and Peter. He closed his eyes, a lump forming in his throat. Had his parents  _ known _ ? Tears welled up in his eyes. He dared to hope they hadn’t but - Derek was going to be sick. He wanted to leave, he was going to go back to the palace and-

Stiles kissed him, gentle and scared. “Say...the merman meets this Prince. Say, he falls in love with him and realises the legend is true, after all. Say-” Stiles turned his face away but Derek kissed his cheek, forcing him to turn back. 

“Say the Prince fell in love with the merman too,” he whispered, pulling Stiles closer. “What then?”

Stiles eyes widened. “ You-” he started, shaking his head. “Then...they have a decision to make.”

“A decision?” 

Stiles shook his head again, the hope Derek saw beginning to fill his face fading instantly. It just made Derek hold on to him tighter. “The Prince has to choose between his family and the merman.” Stiles swallowed, taking measured breaths. “Land or sea. Legs or fins. Them or...me.”

It struck Derek then, what Stiles was asking him, what he was implying. Struck him because he expected it, because he had - 

Hope was too strong a word and guilt flooded him. Looking behind him, Derek traced the outline of his home, his family’s home. He thought of his parents and how every room in it made him think of them; thought of Laura and Cora and how he loved them. 

But they didn’t need him.

If Derek was married off, he would never see them again; that was his role. If he was married - sold - he would no longer he a Hale. He would never be allowed to come home. 

He looked back at Stiles and thought about Peter, about Deaton and what they had done. What made sense now. What had Deaton told his parents about the prophecy?  _ Had  _ he told them? Derek was his Uncle’s pawn and Deaton...had always been right by his side, even before his parents died.

Derek swallowed the bile that rose in his throat.

Peter had always been the one turning every birthday, every holiday, into an opportunity, showing him off, but it had been Deaton,  _ Deaton _ who taught him to respect his role. Deaton who has taught him to accept it, to honour it. It had been Deaton who-

Derek blinked. Maybe he didn’t have to be their puppet anymore. 

“I’d be like you?” he asked, cupping Stiles’ face, something easing inside him. He couldn’t think about his parents, what they might have known. He couldn’t let himself think of anything. Everything he had known, everything he had been groomed to respect and do, had all been based on a lie. If he chose Stiles, maybe, just maybe, he would get the one thing he had always wanted - a happy ending. Derek felt like a boy thinking it, foolish, but he had never been more certain of something either. This is what he wanted. 

Stiles nodded. “I’m sorry.”

“It’s not a bad thing,” Derek laughed, clearly taking Stiles by surprise. “I’m just trying to...understand.” 

“Understandable,” Stiles said, serious, and Derek laughed again. He couldn’t help it.  _ I could have this,  _ he thought.  _ I could really have this.  _

“Would I be able to hear them?” he asked, after a moment. “My sisters? Would I be able to hear them, the same way you sometimes hear your family?”

“Yes,” Stiles said. “But they wouldn’t be able to talk back. Not unless they came down here. Even then, I wouldn’t know...how you’d react. I’ve never heard of a human becoming...one of us.”

Derek nodded. “I should go back, tell them.” He knew he should give his sisters that but is Peter or Deaton caught him...he shook his head. He couldn’t go back. 

Stiles gripped at Derek’s shoulders. “You can walk away. You aren’t bound to me, Derek. No matter what some silly prophecy says. It’s not your fault I was-”

“Stiles.”

“-chosen for you.”

Derek could see this was killing Stiles and yet, he was giving Derek the option anyway; he was telling him to leave. It was more than anyone had ever given him. No-one, not even his parents, had given him a choice before. Especially not when it came to his future

“I only wanted to let you know,” Stiles lowered his head, “in case it was something…in case this could be something. That’s all. We can...we can just continue as we are, if you like. I’d be - I’d be happy, with just that. I promise.” 

_ In case this could be something. _

“It already is something,” Derek whispered, taking Stiles by surprise again. He smiled; the possibility, the  _ knowledge _ of something - something more - taking hold of him, filling him up. Stiles was the first thing he loved that he had never been told to love. He wanted this.

He couldn't stop smiling, even if he wanted to.

“I don’t walk to walk away,” he said. “I want to swim.”

Derek watched, instead of felt, as Stiles’ entire body began to glow, like he was being lit up from within. It was beautiful and Derek slid reverent fingers down Stiles’ arms, gasping. There were scales there. He couldn’t see them but he could feel them and his heart bloomed with affection for reasons he couldn’t explain. 

“Are you sure?” Stiles asked, eyes wide, searching.

“Yes.”

“ _ How _ sure?” 

“As sure as I know I love you,” Derek grinned. “As sure as I know I want to find out where this goes, what we could be.” 

“I don’t know how to reverse it, should you change your mind weeks or years from now.”

“I won’t change my mind.”

“You might.”

“Believe me,” Derek whispered, running his nose along Stiles’ cheek. “I won’t. Can’t. My heart forbids it.”

Stiles grinned, ducking his head. “Sap.” 

“Your sap.”

Stiles rolled his eyes. “I’m going to pull you under now, okay?”

“Okay.”

Derek tried to pull away on instinct, the moment Stiles dragged him down, right to the bottom of the lake, but the moment Stiles kissed him, stopping the water from getting in, Derek felt himself breathe again. Fumbling with Derek’s clothes, Stiles hastily ripped them from him, kissing him deeper, until Derek realised he was beginning to breathe for himself.

Smiling, Stiles ran his hands down Derek’s arms reassuringly, before looking down. Following his gaze, Derek watched, little by little, as his body begin to change, growing tight, his legs knitting themselves together; a blue, electric current wrapping itself around them until Derek was looking at a tail. 

_ His _ tail.

“It’s blue,” Stiles mouthed, grinning. Even though the words were silent, Derek still heard them in his head.

_ Can we talk like this?  _ Derek asked silently. Stiles nodded in return, kissing Derek again.

Derek tried to kiss back but he was too distracted. He had a tail. He wanted to touch it- wanted  _ Stiles _ to touch it- but a great boom from above tore his attention away. Looking up, he watched as the wall began to open - fall, really - revealing a vast ocean that wasn’t dark, nor frightening, but bright and endless. It was a picture, lifted straight from a storybook and Derek gasped, mesmerised by the sight. 

Beside him, Stiles was frozen. “I didn’t think-” he began to say, but before he could finish Derek nudged him forward. Stiles had spent too long here If it was him, Derek knew he wouldn’t want to waste another second looking when he could go. As always, though, Stiles continued talking, hands flailing as he began to swim forward “I didn’t think I’d ever-” he exclaimed, turning one way and then another. This way and then that. “I didn’t  _ think, _ ” he yelled, turning back to look at Derek. “I - I get to go  _ home.”  _

Derek laughed. “You didn’t know?” he called out after him. Stiles shook his head, still in shock and Derek laughed again.

He was leaving his family and he knew there were going to be days he missed them - there would never be a day he stopped thinking about them - but Stiles, after all these years, was finally getting to return home and that alone made Derek feel more at home than he ever had before. He was about to be part of a family. Stiles’ family. Derek had been able to give him that and when he swam out after him, right into his waiting arms, Derek couldn’t help but feel, for the first time, that everything was going to be okay.

**Author's Note:**

> My [ tumblr](http://pale-silver-comb.tumblr.com/) in the fathoms below!

**Works inspired by this one:**

  * [merman sex maaaaaan](https://archiveofourown.org/works/4039108) by [PrincezzShell101](https://archiveofourown.org/users/PrincezzShell101/pseuds/PrincezzShell101)




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